Quadri-phase low pressure method for partial liquefaction of coal



April 19, 1966 M. GA HUNTINGTON 3,247,092

QUADRI-PHASE LOW PRESSURE METHOD FOR PARTIAL LIQUEFACTION OF COAL FiledMarch 19, 1963 LD L; I IJ 5 6o lis TRAcTloNATTNG l SYSTEM i |66 LL! 5E2! g Zd. E# j+- i E D Z Q LT :D j Q S E 22 Zu.: E?

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MORGAN G. HUNTINGTON CHAR 8T ASH ATTORNEYS1 United States Patent O3,247,092 QUADRl-PHASE LUW PRESSURE METHD FR PARTIAL LTQUEFACTIN F CUALMorgan G. Huntington, Washington, DC., assigner, by mesne assignments,to Pyrochem Corporation, Salt Lake City, Utah, a corporation of UtahFiled Mar. 19, 1963, Ser. No. 266,255 The portion of the term of thepatent subsequent to (let. 22, 19%, has been disclaimed 14 Claims. (Cl.208-8) This application is a continuation-impart of my allowed copendingyapplication Ser. No. 41,679, lfiled July S, 1960, now Patent No.3,107,985.

This invention relates to a quadri-phase method for the recovery of themore readily liquefiable petrographic constituents of coal underrelatively low pressure hydrogenating conditions and to apparatus forcarrying out this method.

This invention relates to continuous drying, destructivehydrodistillation and hydrocarbonization of coal and other solidhydrocarbonaceous material. More particularly, this invention concerns acontinuous multi-stage pressurized coal hydrodistillation system in avertical vessel. The system includes the functions of coal drying,p-reheating, `destructive distillation with coincidental mildhydrogenation and immediate vapor phase catalytic hydroreining andhydrodealkylating of the condensable volatiles, and coincidentalredistilling, hydrorefining and hydrodealkylating of re-cycled heavybottoms and selected fractions with whatever entrained solids, partialcombustion of char to furnish heat to the system, and thermal crackingof recycled methane to produce elemental hydrogen.

The destructive distillation of coal by heating in the absence of air iscarried on for the production of coke, gas, tar and oils, and otherby-products. There have been a large number of different approaches tothe carbonization of coal, most of which attempt to accomplish thedestructive -distillation of the coal and to maximize the recovery ofcoal tars, and at the same ltime to produce a minimum of uncondensablegases `and of solid residue. There are also a number of different, butcomplex and expensive, approaches to the total liquefaction of coal suchas high pressure hydrogenation and solvent extraction.

The present quadri-pbase method of coal liquefaction is devised as aneconomic and technical compromise between the mechanically complex andeconomically impractical systems which are 4aimed at the totalliquefaction of the coal by high pressure hydrogenation, and theprimitive, unsophisticated and equally economically unsound destructivedistillation of coal commonly known as low temperature carbonization.

The present invention provides means for thermally cracking whateverpermanent hydrocarbon gases may be distilled from the coal and therebymaking avai-lable to the system all of this hydrogen in its elementalstate. As is known in the art, most bituminous coals have two or threetimes as much surplus hydrogen as is required to hydrorefine the primarydistillate into hydrocarbon cornpounds consisting only of carbon andhydrogen and to saturate the more reactive molecules. Therefore, it isthe purpose of this quadri-phase method to substantially increase theyield of liquid distillate over what is normally considered the FischerAssay volumetric yield of condensable liquid distillate, based solelyupon the thermal destruction of the coal in the absence of air.

Low temperature coal Itars would be practically identical to somenatural crude naphthenic petroleums, if it were not for the fact thatcertain chemical functional groups are attached to most of thehydrocarbon molecules. These chemical functional groups of oxygen,sulfur and nitrogen alter the primary hydrocarbon molecules and promotethe combination and complexity of molecules, and thereby so complicatethe entire tar r-elining problem as to render it almost insolublewithout extensive high pressure catalytic hydrogenation as is describedin Bureau of Mines Report of Investigations 6124, Hydrogenation of PitchFrom Low Temperature Carbonization of Coal.

AIt is emphasized that prior known proposed processes which distillliquids from high volatile coals or perform high pressure hydrogenationretain a considerable proportion of the troublesome chemical lfunctionalgroups of oxygen, nitrogen and sulfur in the product oil. 'Extensivecatalytic hydrogenation and hydrogenolysis are, therefore, necessarybefore the iinal refining into saleable products may be accomplished. Itshould be further emphasized that once the coal volatiles have beenallowed to condense from the Vapor phase, polymerization andinterrnolecular lreaction produces a tar which is at least as diicult tohydrogenate as the original coal.

The coal still system of this invention eliminates the chemicallytroblesome functional groups of oxygen, sul- -fur and nitrogen by thecoincidental, continuous hydrogenation and by the subsequent catalyticsurface hydrogenolysis of the primary volatile matter as it is distilledfrom the coal at system pressure and before it condenses from theinitial vapor phase.

The total gasification and liquefaction processes lead to the synthesisof petroleum substitutes and the yield of products such as gasoline,diesel fuel, oil, lubricants, etc. At the present state of development,the total coal liquefaction systems are expensive to construct and tooperate and while capable of producing satisfactory petroleumsubstitutes from coal, their present product cost is too high to becompetitive with natural petroleum. This invention goes beyond thesimple destructive distillation process which is common to practicallyall the known coal carbonization systems, but does not go as far as thetotal synthesis and liquefaction systems.

In all of the known coal gasification and carbonization systems of theinternal-ly fired type the products of combustion inevitably mix withthe primary volatile matter and the presence of substantial partialpressures of CO, CO2 and H2O aifect the character of the products. Thisis undesirable lparticularly when the direct utilization of hydrogen isof paramount importance since an expensive separating step then becomesnecessary to recover specific constituents from the mixed gases. It isan important object of this invention to provide a method for coaldistillation and gasification in an internally fired retort withoutmixing any products of combustion with the primary volatile matter, in amanner similar to my allowed copending application Ser. No. 41,679.Therefore, the uncondensable gases which result from the destructivedistillation of coal, mainly hydrogen and methane, are continuouslyavailable invpractically a pure state and after removal of ammonia,hydrogen sullide and |water, can be re-cycled through the system,including a heat exchange portion thereof, while at the same time there-cycled methane and whatever other hydrocarbon gases are dissociatedinto hydrogen and colloidal carbon before entering the coking anddistillation zone. With this arrangement, practically all thehydrocarbon gases can be made available for cracking into hydrogen andessentially no other gases are present to lower the partial pressure ofhydrogen.

An important object of -this invention is to provide an internallyheated coal distillation and partial liquefaction system in whichpractically all of the distillable, uncomb-ined hydrogen which wasoriginally present in the coal is conserved without dilution withcombustion gases and is available at system pressures. That is, sincethe products of combustion utilized to heat the system are not mixedwith the coal being distilled, -they do not mix with the primaryvolatile matter evolved. The uncondensable gases of the primary volatilematter are principally hydrogen and methane, and may include C2 and C3gases. These hydrocarbon gases may then be cracked in the heat exchangeportion of the system as the thermal carrier gases are re-cycled throughthe hot char below the combustion zone so that no hydrogen need beconsumed in the incidental production of light hydrocarbon.

It is also an object of this invention -to provide for hydrogenationcoincidental with the destructive distillation to produce a tar which ismuch higher in hydrogen and which is practically completely free ofsulfur and oxygen while at the same time the spent char itself will bedesulfurized and a substantial part of its nitrogen content recovered asammonia. Since hydrogen is actually the thermal carrier fluid which, inthe system of this invention, must raise the temperature of thepreheated, dried coal from about 650 F. to 1600 to 1800" F., and sincethe thermal carrier hydrogen mixed with the primary and secondaryvolatiles and with nothing else, the hydrogen leaving the retort exerts80 -to 95 percent of the system pressure while that of the combinedprimary `and secondary (volatiles from contact coking of the re-cycledheavy bottoms) volatile matter, exert but 5 to 20 percent of the systempressure of l5 to 30 atmospheres.

The coal utilization concept of this invention presents a novel methodof skimming the oils from high volatile coals, or any mixture of coalsin which the oxygen to hydrogen ratio at 650 F. does not exceed three toone, such that all of the coals hydrogen which is uncombined in C3 andheavier compounds is conserved at substantial pressure and in suchpurity and amount as to accomplish the complete, economic hydrogenolysisand hydrogenation of the condensable volatile matter. In this method thelow volatile char (either gasified or pulverized) may be utilized forthe generation of electric power, and much of the atmospheric pollutionnormally resulting from the utilization of sulfurous coal `can beeliminated.

All of the known prior coal carbonization systems have rigidrequirements for the type and size of coal which may -be used. It is anobject of this invention to provide a continuous system for thedistillation and carbonization of coal which may operate on varioustypes of coal irrespective of their agglomerating and ash fusionproperties. Also, because of the particular construction of the systemusing gyratory shelves to feed and to support the series ofzone-separating beds of broken solids, controlling the amount of coaland char on each gyratory shelf and uniformly feeding the solids overthe periphery thereof into -a uniform annular cascade, any coal whichtends to coke or agglomerate and to form scabs on the retort walls maybe broken off by the gyrations of the supporting shelf and passedthrough the system. Further, any large agglomerated chunks too large topass will be broken down as they are fed over the periphery of theshelf. The structural features of the gyrating shelf system per se aredisclosed in my allowed and co-pending application Seria-l No. 17,293(Series of 1960), filed March 24, 1960, now Patent No. 3,083,471.

In general, the capital investment in coal carbonization and processingplants is quite high and the interest on the investment plus thedepreciation usually far outweights the direct cost of operation.Obviously, for any such process to succeed, the net sales of allproducts must exceed by a comfortable margin the cost of the coal plusthe operation and investment charges. However, at least for the present,i-t is evident that the entire operational cost of any coal skimmingprocess must be borne by the revenue from the sale of the distilledliquids, since the monetary value per heat unit of the solid fuelresidue and of surplus gases for steam raising is little different fromthat of the original coal. Therefore, the economic justiiication of anysuch process must hinge upon the enhanced yield and value of its liquidproducts. The only chance for commercial success of such a process willdepend entirely upon the feasibility of producing a petroleum equivalentproduct at a low cost and which can be refined into gasoline, jet fueland diesel fuel in existing reneries.

It is unlikely that any very large new market can be developed for theprincipal chemicals historically derived from coal tar. Moreover, thesechemicals -are presently manufactured more cheaply from petroleumrefinery byproducts than from coal. Further, it is evident that the onlyvery large outlet for special liquid fuels is that of the four millionbarrel a day demand of automotive and `aircraft fuels.

The attractiveness of this specialty motor fuel market becomes at onceapparent when one compares the current price per million B.t.u. formotor fuel with the price per million B.t.u. for coal (motor fuel is 5times as expensive). The economic feasibility of this quadri-phaseprocess for the partial liquefaction of coal becomes possible -throughincreasing, by ya factor of five or more, the market value of someone-fifth of the coals initial caloric content.

This process invention provides the means of substantially augmentingthe manufacture of high octane motor fuel from petroleum more cheaplythan such increase in quality motor fuel production can be obtained frompetroleum alone. Furthermore, the quadri-phase partial liquefactionsystem involves a lesser overall investment than is currently requiredfor finding, developing, producing and refining of new pet-roleum byitself into motor fuel Iof comparable quality.

The basic knowledge of coal chemistry and of chemical engineeringprocessing has developed to the stage at which greatly improvedtechniques are available for converting coal into more convenient formsof fuel and chemicals. Liquid fuels, chemicals, gases and coke can beproduced from coal by the use of modern hydrocatalytic methods whichemploy poisoning resistant catalysts using the techniques of moderncatalytic petroleum refining. Coal re- `fining hydrocatalyticprocessin-g applies catalysts in the form of hydrosolvation,hydrogenolysis, hydrocracking, hydroalkylation, and similar reactionswith hydrogen to produce liquid fuels in the gasoline boiling range. Thewide use of hydrocatalytic processing methods by the petroleum andchemical industries and their applicability to coal processing is wellknown. Commercialization of c'oal processing by such methods has not yetproven economically feasible.

The simplest and by far the least expensive of all processes which wouldextract liquid fuels and chemicals from coal is destructivedistillation. Parenthetically, the chief objective of commercial hightemperature carbonization of coal in America today is the production ofmetallurgical coke. Byproductliquid fuels and chemicals are currently ofminor and quite incidental economic importance to the metallurgicalfuel. Practically all of these hitherto essential coal tar chemicals cannow be produced more cheaply and conveniently from petroleum as refineryby-products.

Many attempts have been made toward commercializing flow-temperaturecoal carbonization processes which would yield a greater amount ofliquid fuels and organic chemicals and at the same time, produce asmaller proportion of low Value, solid residual fuel. All of these priorefforts toward the commercialization of low-temperature carbonizationhave failed economically for these chief reasons:

A. The coke or char produced by such systems is no more valuable thanthe original coal and, therefore, it can bear no part of the processingcost. Earlier attempts to commercialize such carbonization processeshopefully it ascribed an improved value to smokeless, high volatilechar, but the demand for such premium solid fuel was never firmlyestablished.

B. The condensable volatile matter distilled from coal contains a verylarge number of different interreactng organic compounds and thecharacteristics of such coal tars vary between Wide limits dependingupon the conditions imposed by the system of carbonization. No such lowtemperature tar has found acceptance as a commercial source of organicchemicals.

C. More than half of all coal tar distillates constitute a very highboiling refractory rubber-like polymer called pitch (The distillate ofthe present process invention contains no pitch at all.)

D. The throughput rates of coal per unit of capital investment have beenlow and maintenance costs have proved to be excessively high.

The characteristics of the oils and tars produced and the nature of thecompound which result from the destructive distillation of coal arespecifically unpredictable without statin-g a number of conditions underwhich the carbonization is performed. The more important of theseconditions are:

(l) The method of retorting the coal to effect carbonization and thephysical preparation and condition of the coal. That is, whether, (a)the retort is externally heated; (b) the retort is internally heated;(c) the coal is heated en masse and whether batch charging or continuouscharging is employed; (d) whether the coal is ground and dispersed in athermal carrier or thermal transfer gas; (e) whether the coal itself iscatalyzed; (f) whether the coal particles are saturated or coated with ahydrogen donor such as Decalin or tetralin or coated by hydrogentransfer agent such as phenanthrene; (g) if the ground coal is in thedispersed phase, whether the thermal carrier gas fiow concurrently orcountercurrently with the coal; (h) whether the partial pressure of thevolatile matter is above or below its critical pressure and therefore,whether or not the heavier boiling constituents can pass into the vaporphase before being thermally destroyed during carbonization.

(2) Temperature of the heat source, that is, (a) the temperature of theretort Walls if internally heated; (b) the temperature of the thermalcarrier medium if internally heated.

(3) The residence time of the coal Within the carbonizing environment,i.e., the rate of evolution of the volatile matter.

(4) The size of the coal particles if `ground and the temperature towhich the outer part of the coal particle (or the coal mass if unground)rises before all of the volatile matter is expelled from the coolerportion of the particle or the mass.

Although essentially all of the condensable volatile matter is expelledfrom coal between the temperatures of 700 F. and 900 F. whendestructively distilled under conditions at which the partial pressureof the volatiles does not exceed atmospheric pressure, the character andthe amount of the primary condensable matter may be drastically altered,depending mainly upon the several conditions to which the vapors aresubjected following its distillation from the coal:

(a) The temperature to which the primary volatile matter is raised afterit is evolved and the length of time the vapors are held above thevaporizing temperature.

(b) The type of surface with which the vaporized distillate comes incontact and the length of time such contact continues.

(c) The atmosphere during the carbonization, that is, the extent towhich the partial pressure of the condensable volatiles is reduced bydilution with hydrogen, methane and other `gases such as hydrogensulfide, water vapor, carbon monoxide, carbon dioxide, and ammonia,during distillation and while the volatile matter vapors remain atreaction temperatures.

Vapor phase catalysis or" the hydrogen entrained volatiles prior toinitial condensation is the third and most important means of producinga coal distillate of desirable qualities. The character of the catalyst,the time of contact of volatiles with a catalytic surface, thetemperature and the pressure during catalysis are the controllingvariables. Vapor phase catalysis can affect the coal distillate in anumber of ways including the removal of oxygen and sulphur and most ofthe nitrogen as their respective hydrides, producing an essentiallyneutral oil; rings can be caused to open or to condense and chaincompounds can be caused to vform rings; cycloparafiins can bedehydrogenated to form aromatics and aromatics can hydrogenate to formcycloparafiins; alkyl groups can be transferred from one ring compoundto another such as the formation of two mols of toluene from one mol ofxylene and one mol of benzene; at higher temperatures, all aromatics canbe completely de-alkylated so that the ultimate products, beforecomplete carbonization into carbon and hydrogen, are benzene,naphthalene, anthracene, chrysene and their homologs.

As indicated above, vapor phase surface catalysis of the coals volatilematter immediately following destructive distillation of the coal,offers a wide range of control over the character of the quadri-phasesystem distillate. For example, over certain combinations of catalystsarranged in sequential fiuidized beds and subject to separatetemperature control, the following reactions can be accelerated towardequilibrium Within a single continuous hydrogen entrained vapor stream:

(l) Sulphur, oxygen and nitrogen can be removed as their respectivehydrides. Oxygen can be eliminated completely, thereby removing all taracids and sulphur can be reduced below parts per million. Noncyclicnitrogen can also be eliminated and the remaining stable heterocyclicnitrogenous compounds such as pyridine and its homologs arewater-soluble and/ or soluble in acid solutions and are separatedthereby.

(2) Cycloparafhns (naphthenes) can be dehydrogenated to aromatics attemperatures above 900 F.

I (3) Benzene can be recycled and alkylated to ethylbenzene and totoluene by the partial dealkylation of the higher homologs.

The quadri-phase system of partial coal liquefaction offers a furthermeans of product control: Dealkylation of alkyl naphthenes and theelimination of close boiling nonaromatics can be coincidentally effectedby recycling the 207 2l7 C. fraction and the 2l9270 C. acidscrubbedfraction into the high temperature distillation Zone by spraying thesefractions against the incandescent carbon cascade at the horizon atwhich it has reached `temperatures in the order of 1200 to l600 F.Residual petroleum refinery stocks can also be injected into theincandescent carbon cascade to accomplish contact coking and therecovery of aroma-tic compounds.

The present quadri-phase method and apparatus for low pressure coalliquefaction provides for the fiash melting of coking coals and theliquid and vapor phase hydrogenation of active sites formed by thethermal breaking of oxygen and sulfur intermolecular fonds, andsubsequent distillation of the more easily liquefiable petrographicconstituents of ground coal while it is falling freely countercurrentlywith respect to a stream of heated hydrogen at moderate pressure.

This process also concerns the manner and the sequence of heating thecoal particles in order to autogenously create on each particle a liquidsurface film by melting, and into and upon which liquid film is absorbedand adsorbed hydrogen and continuously distilling off the surface filmof liquid and removing `the same from the system as a vapor. Thisprocess may also include the recycling of phenanthrene and othercondensed nuclear compounds which, when melted, are favorable to theabsorption and transfer of hydrogen to coal particles.

This process particularly concerns the effective increase of hydrogenconcentration by adsorption and absorption upon the particle liquidsurface. The process also includes the autogenous formation of thisliquid vehicle as a lmolten or liquid iilm upon the particle surface andits continuous removal from the particle by distillation into thermalcarrier hydrogen and the subsequent and immediate vapor phasehydrogenation of the whole stream of volatile matter upon one or moresequential beds of selected catalysts.

This invention further provides automatic control of the liquid phasetemperature by the absorption of the exothermic heat of hydrogenation asenthalpy of vaporization, thereby minimizing disproportionatingreactions and the formation of unreactive coke.

This process produces a primary neutral oil from the two-stagehydrogenation of coal, which oil contains less than two hundred partsper million of oxygen and sulfur and less than one percent ofasphaltenes (organic material soluble in benzene but insoluble in normalhexane).

This process is entitled Quadri-Phase Method of Low Pressure CoalLiquefaction because during the free fall of particles of ground coalagainst the rising stream of hot, pressurized hydrogen in addition tothe solid phase, liquid vapor and gaseous uid phases all existsimultaneously in or near each particle as it changes from dry coal tononreacting char:

(1) The Solid Phase-because the coal enters the system dry and withoutliquid vehicle and exits from the system as dry, low volatile, lowsulfur char.

(2) The Lz'quid Phase-because a molten liquid phase is formed primarilyby the melting of the outer surface of each coal particle. Liquefactionis promoted by the rapid surface adsorption of hydrogen, some of whichbecomes chemically combined, reducing both the melting temperature andthe boiling temperature of the liqueable coal constituents.

(3) The Vapor Phase-As the liquid surface film rises in temperature toits boiling point at system pressure, it is continuously distilled as avapor into the thermal carrier stream of hydrogen until nothing but theunreactive char remains with its original ash and nonvolatile catalyst.

(4) The Gaseous Phase-Hydrogen is the thermal carrier and the principalreacting uid.

This process is aimed primarily at the partial liquefaction of coal'under moderate pressure using the hydrogen initially contained in coalto the fullest extent and to the best advantage in order to produce themaximum volume of useful liquid in a system normally operating below 500p.s.i. except when more severe hydrogenating eifects should be desired.

Although this process of coal utilization goes somewhat beyond thesimple `destructive distillation processes which are classical andcommon to practically all coal carbonization systems, this process doesnot go so far as total coal liquefaction as in the Frederick Bergiushigh pressure coal hydrogenation process. Rather, the presentmultiple-phase method of low pressure coal liquefaction is, in effect,an autogenous hydrogenation system which maximizes the advantages of thenatural phenomena of destructive distillation performed in a hydrogenatmosphere at moderate pressures.

Also, in one embodiment of the present method, the degree to whichdisproportionating thermal reactions take place is controlled and therate of chemical combination of hydrogen with coal is promoted by thejudicial use of specific catalysts and hydrogen transfer agents coatingthe ground coal particles.

This process is, therefore, a median method which might be classified aslying about midway between simple coal carbonization and the verycomplex high pressure hydrogenation of the whole coal.

The present method also accomplishes what neither of the two earlyconcepts contemplate by yielding a reiinable, neutral oil from coalwithout tar acids or tar bases as the direct product of the process, andwithout the form-ation of any refractory pitch complex.

Other objects of this invention will be pointed out in the followingdetailed description and claims and illustrated in the accompanyingdrawings which disclose, by way of example, the principle of thisinvention and the best mode which has been contemplated of applying thatprinciple.

In the drawing:

The single figure is a semi-schematic illustration of a coal stillcapable of carrying out a preferred embodiment of the process of thisinvention.

In general, the schematic representation of the coal still includes asingle, continuous, pressurized, vertical vessel ltl'having means formeasuring and charging coal thereinto and discharge means for removingthe char or ash therefrom. The coal still, between its top (solidmaterials charging) and its bottom (solid materials removal), is dividedinto Ia number of zones for accomplishing various functions. The singlecontinuous, pressurized vertical vessel 10 performs various functions infour different zones. The zones are labeled on FIG. l of drawings. Thezones include a concurrent ow drying and preheating zone A, adistillation zone and thermal treatment B, a partial combustion zone C,and a heat transfer and methane cracking zone D, somewhat similar to theallowed column of solid fuels in accordance with the function of thevarious zones.

Zone A performs the triple function of drying, preheating and removingcarbon oxides from the crushed raw. coal. The heat for zone A isfurnished by the sensible heat of the high temperature flue gas from thepartial combustion of char in zone C. The hot flue gas llowsconcurrently with the raw fuel cascade and effects the preheating of thecoal to 650 F. without any destruction of the coal substance beyond theexpulsion of water and carbon oxides.

Zone B performs the function of distilling olf the primary volatilematter and heatingthe coal completely through its plastic range within afraction of a second while the coal particles are in suspension andwhile they are cascading against hot ascending hydrogen preheated incontact with incandescent char in zone D below. Little or noagglomeration of the coal particles occurs, and in the pressurized,vessel 10 the volume of the char increases only about live times ascompared to some times which is possible in such systems operated atatmospheric pressure. Also zone B allows for thermal treatment ofrecycled products and contact coking of heavy bottoms and mixed groundcoal, if desired.

Zone C is a combustion chamber within which the partial combustion ofthe char to carbon dioxide is achieved in two stages, i.e., some carbonmonoxide is generated inthe fuel cascade by the injection of a limitedamount of oxygen, then the carbon monoxide is separated physically fromthe solid carbon and subsequently is burned to carbon dioxide by asecondary injection of oxygen. About one-half of the heat of thesecondary combustion of carbon monoxide to carbon dioxide is radiatedback to the fuel cascade and about half is conveyed to zone A assensible heat of the ue gas leaving the combustion zone D. A preferredpartial combustion zone is shown in my co-pending application Serial No.186,920 tiled April l2, 1962.

The temperature of the char and the temperature of the flue gas areregulated by the rate of oxygen admission into the combustion zone. Theapportioning of the sensible heat content of flue gas in relation to thesensible heat content of the char is controlled by varying the oxygenenrichment by the degree of preheat of the combustion blast.

As is shown in FIG. l, when necessary char is recycled through thecombustion and heat transfer Zones C and D. The purpose of recycling thechar is to increase the total heat capacity of the fuel cascade throughthe lower two functional Zones by a factor of about four, as isexplained in detail hereinafter. This becomes necessary only in veryhigh volatile coals when the low volatile char is less thanSS or 60percent of the initial moisture and ash-free coal.

Zone D performs three functions: It thermally cracks recycled methane incontact with cascading, incandescent char; it transfers heat from theincandescent char, heated in the combustion Zone D above to the recycledhydrogen and to products of thermal disassociation (hydrogen and carbonblack) which become the thermal carrier media for zones C and B above;it also recovers useful heat from the low volatile spent char.

The char produced in the system is typical of that formed by droppingground, melting coal against streams of gases heated above l500 F. withthree very important and distinct improvements: 1t has a higher bulkdensity, lower sulfur content and greater surface activation.

Each of the zones contains one or more gyratory shelf feeders for solidmaterials and zone gas zonal gas diffusion barriers. Each gyratory shelfis of the nature disclosed in my allowed cti-pending application SerialNo. 17,293 led March 24, 1960 and reference may be had thereto for afurther description of the details of the mechanical features of eachgyratory shelf. The gyratory shelves dening the concurrent flow dryingand preheating zone A are shelves 12 and M. Shelf 12 serves as the solidmaterial feeder shelf for the entire system. Shelves 12 and 14 carryenough solid materials thereon so that they function as gas separatingbeds. In other words, the solid unsorted material on the shelf iscontrolled in depth and density such that gaseous fluids will notreadily flow therethrough and will not pass from one zone to another insignificant amounts at thesmall differential pressures which areautomatically maintained. The distillation thermal treatment Zone B maybe detined by separating beds on gyratory shelf units 14 and 16.Gyratory feeder unit 16 likewise includes solid materials carriedthereon of such depth and density to function as a separating bed andalso to prevent ow of gaseous fluids between the zones above and belowthe bed. The partial combustion zone C is defined gyratory feeder shelfunits 16 and 1S. The particular construction and operation of thepartial combustion zone is clearly set out in my co-pending applicationSerial No. 186,920 led April l2, 1962 and now Patent No. 3,190,245.Gyratory shelf feeder unit l@ also carries a separating bed foreffectively separating the combustion and gas producer zone C from thenext lower zone which is the heat transfer and methane cracking zone D.

For the sake of simplicity only, the gyratory shelves de- -ning theseparation of the various zones have been shown.

It will be understood, however, that additional gyratory shelves can, ifdesired, he utilized with any Zone, although the additional gyratoryshelves would not carry the materials in such a depth and density thatit would serve as a gas separating bed.

It is noted that the separate functions are performed in zones which areseparated within the continuous vertical vessel by beds containing deeplayers of crushed char or coal which substantially prevent the flow ofgaseous fluids between adjacent Zones. The beds themselves are comprisedof unsized, unsorted solid material through which heated gases simplycannot pass in volume at existing small pressure differentials.

Control of the depth of solids on the separating beds may beaccomplished by any suitable known type of level sensing c-ontroller,such as a gamma ray level detector adapted to control solids being fedto the separating beds. Two positionable gamma ray level detectors canbe provided for controlling the maximum and minimum depth of eachseparating bed.

CFI

At the top of the vertical cylindrical retort is a measuring bin 20which is charged with only enough raw, crushed coal so that its entirecontents may be dumped into a charging lock 2.2, thus' leaving bellvalve 2li completely clear for unobstructed closing. After the raw coalis dumped into the charging lock 2.2 and valve 24 is closed, the coalmay be pressurized by closing a valve 26 and opening a valve Z3 allowingnon-explosive ue gas from flue gas receiver 32 to flow into the charginglock through conduit 30 at system pressure. The charging loclt 22 isclosed at the bottom by hopper-like arrangement and a movable bell valve34. Thus, when the charging lock contents are pressurized, valves 26 and2S are closed and bell valve 34 may be opened to dump the pressurizedcharge of solid carbonaceous material on to the system gyratory feedershelf l2. After dumping the valve 34 may be closed and the vent valve 26opened to allow the pressure in charging lock 22 to vent to atmosphericthrough conduit 36. 1n the pressurizing of charging lock 22 with theflue gas, the purpose is not only to use a gas more readily availableand cheaper than steam but the ue gas will be entirely non-explosivesince it contains principally products of combustion.

Below the system gyratory feeder shelf 12 in zone A, there may beadditional gyratory shelves (not shown) and there may be a core-baffle3S or similar means to ensure that the falling cascade is generallyannular in section. Leading into the top of zone A below the gyratorysystem feeder shelf l2 is an inlet itl for hot flue gas and there may bea plurality of inlets (not shown) equally spaced to ensure good solidand gaseous material contact. At the bottom of zone A, is a conicalcollector hood 42 for removing the ue gas after its heat exchangepurposes in the drying, deoxidizing and preheating Zone.

Below the separating gyratory shelf 14 in the flash carbonization zoneB, there is a conical offtalre hood 44 for the volatile matter distilledfrom the coal as well as thermally treated recycled products of theprocess as will be described. Also in zone B are a plurality of spreaderinlets 45, 46 and 47', for introducing recycled intermediates forthermal treatment in an atmosphere of hydrogen plus heavy 4bottoms forcontact coking and for redistillation, together with whatever solidsthey may include or have included therein. The inlets 45, i6 and i7 inzone B allow for different degrees of severity of thermal treatment,ranging from merely redisti-llation into the vapor.

phase at 900 F. to mild dehydrogenation of naphthenes to aromatics inthe central injection, to the lowest injection where the alkylatednaphthalenes are completely thermally dealltylated in contact withincandescent carbon. The introduced liquids (and gases) are spread outto contact the annular cascade by similar baffles dit and the cascade iskept in annular shapeby a core baffle 50 which also functions to preventthe solids from boiling up at the bottom of zone B. Also near the bottomof zone B, there is an inlet conduit 52 for hot thermal carrier hydrogenand this inlet is arranged so that the hydrogen contacts the entireannular cascade and flows countercurrently thereto. There is also asolid material inlet 54 underneath the separating bed carried on shelf16 and this solid material inlet Se is for recycling char as will hedescribed.

Zone C includes a conical hood 56 with a flue gas offtake 58 at its apexand an oxygen inlet 60 into the lower portion of cone 56 as well asadditional inlets for oxygen and air 62. The operation for accomplishingpartial combustion of char to carbon monoxide and the further combustionof carbon monoxide to carbon dioxide is per se not a part of thisinvention, but rather is covered in copending application Serial No.186,920 led April l2, 1962.

Below the gyratory shelf 18 Within the vertical vessel 10 and in themethane cracking zone D, there is a conical hood otftake 6a for hothydrogen. Below the hood is another core baffle 66. Core bafe 66 and theother core baffles mentioned above, would preferably have a diam- 1 1eter such that the clear annular space between the edge of the corebattle and the inside of an insulated and possibly cooled shell of thepressurized vessel, will preferably be one to three feet in width.

Below core baiiie 66 is a collector 68 for recycling a predeterminedquantity of char when the yield of char is less than 60 percent of theM.A.F. Coal and/or when additional sensible heat is necessary formethane cracking, as will be described hereinafter.

At the bottom of methane cracking zone D there may be a hopper 70 closedby a bell valve 72. Alternatively, there may be another system in thesame or adjacent vvessel so that the char may be heated up again andused for gas making as shown for example in my copending allowedapplication, Serial No. 74,907 led December 9, 1960, now Patent No.3,088,816.

Below hopper 70 is an isolating bin 74 closed at the bottom by hopper 76and a `bell valve 78. This isolating chamber 74 enables the char to bedumped in toto into a char lock chamber 80. Char lock chamber 80 issimilarly closed at the bottom by hopper 82 and a bell valve 84. Fluegas from ue gas receiver 32 may enter through .conduit 86 under thecontrol of valve 88 into char lock 80 and may be vented therefromthrough conduit 90 under control of valve 92. The bottom of the vesselmay, if desired, include a hopper 94 for removal of the char productwhich in turn may be used to raise steam or for other industrial fuelingpurposes.

As can be seen from the foregoing, the passage of the solid materials,which consist of ground, unsized coal, is vertically downward in thevessel controlled at various horizons by the gyratory shelves, andincluding when necessary a recycling through the combustion and heatexchange zones, some portion of the char. The recycling of the charincludes in addition to the collector 68, a char conduit 96 which iscontrolled by a star valve 98. Star valve 98 controls the entire feed ofthe recycled char and may be driven from suitable motor controlsinterrelated to the other parameters of the system. The solid materialswhich are fed by star valve 98, enter conduit junction 100 whichfunctions as a heavy .solids trap, and the heavier or coarse materialsfall downwardly into conduit 102 and may be periodically removed byopening a venting arrangement including interlocked valves 104 and 10S.Gas

at system pressure circulated by a fan 106 draws the recycled char fromjuncture 100 upwardly through conduit 108 and deposits it into a gasseparator 110. Within the gas separator 110 the gas is taken off in hood112 and recirculated through line 114 to juncture point 100. Meanwhile,the recycled char falls downwardly through inclined inlet 54 to belowthe level of solid materials on separating bed 16 to be recycled throughthe partial combustion zone C and methane cracking zone D. Thus, thesolid materials iiow vertically downward but are recycled as required tofurnish the heat exchange capacity necessary for the system.

In addition to the solid material ow as described above, there are twoseparate fluid circuits. One of the circuits is that of thermal carriergas consisting essentially of hydrogen, and the other is that ofcombustion flue gas consisting essentially of carbon dioxide and inertgas (nitrogen). Mixing of the carbon dioxide in the hydrogen circuit isprevented by deep separating beds 16 and 18 adjusted by suitablecontrols and a very small counterow of hydrogen into the ue gas circuitis maintained by positive displacement metering of the fluids into andout of the two circuits of the system. The hydrogenous and oxygenatedfluid circuits are separated by the mechanically controlled gyratoryshelf separating beds as described below.

The thermal carrier hydrogen circuit may be described starting with aConduit 116 for recycled hydrogen and methane from a condenser andscrubber and this recycled gas passes through a positive displacementmetering valve 118 through an inlet conduit 120 into the annular cascade12 of freely falling hot solid materials which have left the partialcombustion zone C and have been fed by gyratory shelf 18 through themethane cracking zone D. Methane is cracked into hydrogen and colloidalcarbon in zone D as it flows countercurrently to the hot hydrogen. Thevery hot hydrogen passes ot through oiftake cone 64, ottake conduit 122(which may include a mechanical cleanout 124) and into a knockoutchamber 126 with a bottom outlet valve arrangement 128 for solidmaterials. The knockout chamber 126 for the hot thermal carrier hydrogencontains the hydrogen at a temperature of around 2500" F. and bypassesthe partial combustion zone C to pass the hot hydrogen through conduit52 into the bottom of the distillation and thermal zone B so it ilowscountercurrently with the falling hot annular cascade. As the hothydrogen flows countercurrently with the falling cascade of coal in zoneB, it also flows countercurrently with any recycled intermediates andentrained solids. The volatile matter distilled off the coal, thethermally treated recycled intermediates, etc., ow through offtake hood44 through conduit 130 where it may be mixed with additional hothydrogen from line 132 under the control of metering valve 134.Additional offtakes (not shown) may also be provided at diferenthorizons. The mixture of volatile matter and hydrogen passes into aknockout drum 136 with the bottom valve 138 and with a mechanicalcleanout 140. The knockout drum may contain sized uidized char onscreen139 and the tar in the products passing therethrough will be removed byimpingement on the char. The gases and vapors from the knockout drum136, which includes volatile matter and entrained solids with thermalcarrier hydrogen at a temperature of about 1000 F., passes out line 146to three catalyst chambers in series, these are catalyst chambers 147,148 and 149. Additional hot or cold hydrogen may be admixed into line146 for temperature control through line under control of valve 152.

rlfhe three catalyst chambers 147, 148 and 149 in series perform thefollowing functions on the stream:

Catalyst chamber 147 deoxidizes, desulphurizes and saturates the olens,preferably on a cobalt molybdate catalyst.

Catalyst chamber 148 performs the -function of reforming whichis acommon type of renery operation and which removes hydrogen fromnaphthenes to leave aromatic compounds.

Catalyst chamber 149 has the further purpose of causing an alkylationshift using a third type of catalyst which promotes the transfer 0falkyl groups such as methyl, ethyl, propyl, etc. from one molecule toanother. For example, practically 100% yield is obtainable when benzeneaccepts one methyl group from xylene to produce practically all toluene.

Cool or cold hydrogen from line 142 may be admitted selectively asdesired to each catalyst chamber 147, 148 or 149 through control valves141, 143 and 145 respectively for the purpose of temperature control.

The outlet from catalyst chamber 149 includes a line 154 leading into afractionating system 156. The fractionating system 156 may compriseseveral smaller lfractionators (not specifically shown) known asstrippers. However, since this invention is not concerned with the artof fractionating per se, fractionating system is merely disclosed ingeneral.

From the bottom of the fractionator system 156 a takeoff 174 is providedwith a control valve 176 for pumping heavy bottoms through line 178 intoa selected inlet cone within zone B of the coal still. Additional heavybottoms from the knockout drums may be mixed into line 178 and groundcoal or other solid particulate hydrocarbonaceous material may be addedinto line 178, for example through inlet 180 controlled by valve 182.Also, instead of recycling for contact coking or other thermal 13treatment the bottoms could be removed through line 131 under control ofvalve 183.

The fractionating system will also have a number of other outlets as isknown in the art. Overhead passes out line 158 to conventionalcondensers, gas scrubber-s, etc., as is known in the art. is the factthat a number of different outlets 160, 162 and 164 at the side of thefractionator system represent different boiling range products as willbe `set out in detail hereinafter.

The different boiling range streams which appear in outlets 160, 162 and16d (as enclosed by bracket 166) may be selectively recycled forreheating and revaporization. This is accomplished by selective fluidinterconnections between the fractionator system outlets of bracket 166and zone B coal still inlets enclosed by bracket 168.

Therefore, in order to obviate the use'of pipe stills, recycle streamsmay be sprayed into the cascading `hot carbonaceous material in zone B.Those fractions which require the least thermal exposure, for example,benzene which is being recycled for alkylation say to toluene while atthe same time dealkylating xylene to toluene, will be sprayed into theupper portion of zone C. At the same time, very intense dealkylation ofalkylated naphthalenes require that these compounds, that is, thoseboiling above 218 C. and below 290 C., be recycled into the lower andbottom part of zone C.

The remaining fluid circuit is that of the combustion gases. In thepartial combustion zone C, metered amounts of oxygen and air areadmitted through inlet line 62 from oxygen manifold 184 and compressedair line 186 under the control of metering valves 138 and 120respectively to mix in required proportions for entrance into thefalling cascade for oxidizing the carbon of the coal to carbon monoxide.The carbon monoxide within the combustion cone 56 is further oxidized tocarbon dioxide by oxygen introduced through line 60 under control ofvalve 192 from oxygen manifold 184. The CO2 flue gas at very hightemperatures e.g., around 3000 F., passes from offtake S into a flue gasknockout chamber 194 having an intermittent mechanical cleanout 196 forthe inlet passage and the usual bottom valve 198. Hot flue gas passesout the top thereof through line 200 into inlet 40 in the top ofthedrying, deoxidizing and preheating zone A. The outlet of the gas fromZone A after owing concurrently with the falling annular cascade andpreheating the same to about 650 F. is through outlet offtake cone 42,conduit 202 into a gas knockout drum 2011; at approximately 700 F. Theusual bottom valve 206 is provided as is a mechanical cleanout20. Theflue gas from the knockout drum 204 passes to a cooler and flue gascondenser 210 from where the stream distilled condensate passes outthrough line 212 under control of valve 21e, and the cooled flue gaspasses through outlet 216 under control of metering valve 213 into theflue gas receiver 32 through check valve 220. The gas for carrying andtransporting the char during recycle may be obtained through line 222under control of valve 22d for making up any gas loss in the gastransport.

The operation of the coal still and the process of this invention willnow be described.

The input coal is ground but not sized and may be coated either with acatalyst or a recycled hydrogen transfer agent such as phenanthreneeither sprayed on while liquid or crushed and mixed with the coal.

The optionally pretreated ground coal is dumped into measuring bin 20and then into charging lock 22 by opening valve 24. Charging lock 22 isbrought up to system pressure by closing valve 26 and opening valve 28.Upon attaining system pressure in charging lock 22, bell valve 34 in thebottom thereof may be opened so that the crushed coal from charging lock22 is dumped upon the system gyratory shelf feeder unit 12. After thecrushed coal has been discharged through bell valve 34, the charginglock 22 may be depressurized by closing bell valves 2d Most importanthoweverv 141 and 34, closing valve 28 and opening valve 26 whichdischarges the contained liue gases through line 36 to the atmosphere.The charging lock may be then reloaded as before.

The rate at which the crushed coal is fed off the system gyratory shelffeeder unit 12 or any of the other gyratory feeder shelves is a functionof the amplitude and rate of gyration of each gyratory shelf feederunit.

ln the drying deoxidizing and preheating Zone A, the crushed coal andhot drying tiue gas admitted at 40 mingle in concurrent downward ow. Indrying deoxydizing and preheating ground coal, two primary functions areeffected at precisely limited temperatures. First is the removal ofsuperficial moisture at steam saturation temperature at system pressure.For example, at a system pressure of about 20 atmospheres (300 p.s.i.)the steam saturation temperature is 417 F. A large amount of heat may berapidly transferred to cold moist coal from a very high temperature gaswithout thermal destruction of fine coal particles. If for example, thedrying gas enters the Zone A through line i0 at about 2800" F., thesaturation tem perature of steam at system pressure cannot be exceededuntilpractically all of the superficial moisture has evaporated. At thatsame time, the coal particles must have also risen in temperature to thesaturation temperature of 418 F. At this point, some three-quarters ofthe available heat has been transferred from the drying gas to the coaland to the surroundings and the temperature of the drying gas hasdropped from about 2800 F. to about 1200 F. Therefore, in flowingconcurrently the very hot drying flue gas can at no time have sufficientthermal heat to destroy even the nest coal fragments.

The other function performed in this zone A is the removal of oxygenfrom lower ranked coals as carbon oxides and as water vapor, and thisoccurs primarily between the temperatures of 400 F. and 650 F. withoutsignificant evolution of hydrogen or of hydrocarbons. In thistemperature range many oxygenated compounds break down to form water,carbon monoxide and carbon dioxide. However, it is important that thetemperature of the coal in zone A is n ot raised above 650 F. at whichpoint distillation of hydrocarbon begins because any hydrocarbonevolution in Zone A must represent a net loss to the system.

The elimination of the carbon oxide gases and water vapor before thedistillation and producing the hydrocarbon volatiles is a very importantadvantage and improves the operation for two principal reasons. First ofall, the available hydrogen to carbon ratio of the coal is markedlyimproved and the significance of this increases with the lower ranks ofthe coal. Secondly, whatever carbon oxide gases appear in the volatilestream must be scrubbed from any recycle of gases because their diluenteffect is cumulative. Morever, any recycled carbon dioxide in thermalcarrier hydrogen becomes, to some extent, a reactive oxydizing agent atsystem temperatures and interferes with the production of neutral oil.Therefore, coal enters zone A at system pressure and at a relativelycool temperature. The coal is preheated by incoming flue gas coming inabout 2800 F. and exiting at a temperature of about 700 F. so that thecoal is dried and preheated to about 650 F. as it lies on gyratory shelf14 and this temperature is just below its temperature range at whichevolution of hydrocarbon gases begins to any important extent. Also, thefreed carbon oxides and water vapor will be expelled from the systemthrough offtake 202 and after being cooled, the steam condensated willdrain off through line 212.

The dried, deoxidized, and preheated coal is then fed off the peripheryof gyratory feeder unit 14 into the dis tillation and thermal treatmentzone B. In zone B, a thermal carrier fluid, which consists principallyof hydrogen is passed countercurrently through the annular cascade ofdescending coal to drive oif the primary volatile matter through offtakecone 44 and flue 130.

I have discovered that finely ground melting coal dropping freelythrough heated gases can be carbonized at rates in the order of some50,000 times faster than has been achieved by any system whichcarbonizes coal en masse. Further, the limiting factor of flashcarbonization capacity is the rate at which heat can be supplied to thesystem rather than the rate at which coal can absorb the heat available.

Most bituminous coals melt and many actually become liquid between 700F. and 900 F. However, the plastic condition usually encompasses atemperature range of no more than 100 F. The fact that some coals softento the extent of actually becoming fluid, greatly complicates themechanics of handling coal while it is in the intumescent stage ortemperature range. Sticky coal in the 700 F. to 900 F. temperature rangeadheres to practically all surfaces cooler than 900 F. with which itcomes in contact. Equally serious is the fact that caking coalsagglomerate in passing through the plastic range. The worstsituation, ifheated en masse without movement, strongly caking coals will actuallyform a chunk of solid coke the size and shape of the containing vessel.Even those coals which are not considered strongly caking will tend tomelt in an atmosphere of hydrogen which is the thermal carrier uid inthis invention. However, even sticky coal will not adhere to surfaceswhich are maintained above the thermal setting temperature of about 900F. Furthermore, when dispersed and freely falling, agglomeration isnegligible.

After being dried and preheated and deoxydized in zone A wherein abouthalf the total heat requirement of the system is supplied, the coalbeing fed olf gyratory shelf 14 falls evenly and freely as an annularcascade into a rising column of pressurized hot hydrogen admittedthrough line 52, the hydrogen having sufficient heat capacity per unittime so that all of the coal must pass through its intumescent range andbecome thermally set before arriving at a pile in the bottom of thechamber including the flash carbonization zone B. At the same time, inorder to scale off any scabs which may occasionally adhere to the sidesof the apparatus, large chunks of refractory tirebrick may occasionallybe cycled through the system.

It is also important that high sulfur coal can be used in the system andthe resultant char will be substantially desulfurized. If coal is heatedrapidly in a stream of diluting hot hydrogen as it is in this process inzone B and if the organic molecules of volatile matter which containsulfur are immediately removed from the solid carbon as they are in thisprocess through offtake cone 44 and line 130, the resultant char will bedesulfurized to the extent that a large part of the organic sulfur andhalf of the pyritic sulfur (but none of the sulfate sulfur) is removedwith the stream of volatiles. Much of the remaining portion of pyriticsulfur (FeS) is removed as SO2 and COS during partial combustion of charat temperatures in the order of 2500 F. to 3000 F. in combustion zone C.The resulting char exiting from hopper 94 at the bottom of the vesselafter also being contacted with hot hydrogen in zone D would containonly a small part of the original sulfur of a high sulfur coal and this,of course, is a desirable characteristic of the char for steam raising,metallurgical use and the like.

Falling coal in zone B, ground to pass through a 30- mesh screen can beheated from 650 F. through its plastic range in less than half a secondduring a free fall of less than ve feet against rising hydrogen at 1500F. It is important to note that the coal particles with a terminalvelocity in hydrogen less than the superficial velocity of the hydrogenand which are therefore entrained may be recycled with the recycledheavy bottoms entering through inlet cone 46 in zone B and sprayedagainst descending solids.

The coal entering zone B is preferably of such a neness that itsterminal velocity in hydrogen at system pressure may lie between twofeet and twelve feet per second. For optimum liquefaction, a catalystand/or hyfv drogen transfer agent (phenanthrene) may be coated on thecoal particles in a manner most suitable to distribute the catalyst onthe surface of each particle of coal. The coal, of course, is dried andpreheated in zone A as described above and is dropped into the risingstream of hot thermal carrier hydrogen which partial pressure is fromten to twenty times the partial pressure of the desirable oils in orderthat they may freely evaporate at system temperature and pressure.

As the coal particles drop countercurrently in zone B through thethermal carrier hydrogen, there is established a reaction zone whoseupper limit is dened by the initial melting point of the coal and theformation of a liquid lm on the surface of the coal particles. The lowerlimit of the reaction zone is that horizon in which all the liquidsurface lm has been completely distilled from the particles and onlychar and catalyst remain. The vertical extent of the coal melting andhydrogenation reaction zone is principally a function of fourcontrollable parameters of the system including the inlet temperature ofthe preheated coal particles, the size and size range of the coalparticles, the volumetric heat content of the thermal carrier hydrogenper unit time, and the partial pressure of the condensable volatiles.

In general, the hydrogenation characteristics of various coals can bepredicted by the comparison of the opacity of thin petrographic sectionsand those sections which are more translucent will hydrogenate morerapidly and under milder conditions than those of less translucence. Afurther reliable prediction as to the hydrogen acceptance of thepetrographic constituents of coal may be obtained from the determinationof sulfur, oxygen and nitrogen which may form cross bonding betweensegments of the original coal molecule and which bond may be thermallybroken to form active sites which readily hydrogenate. The thermalbreaking of such cross bonds is the primary mechanism by which theoriginal coal molecule yields liquid fragments which have molecularweights in the order of one tenth of the coal. Hydrogenation of theseactive sites increases liquefaction and pressures below 500 pounds persquare inch. v

The contact coking of recycled bottoms and mixed solids may also beaccomplished in zone B. By introducing the bottoms into the lower partof Zone B for some thermal treatment secondary distillation up to l800F. is accomplished and redistillation and contact cokng of selectedrecycled fractions with whatever entrained solids may be therein, isalso accomplished. Furthermore, the tars from the various knockout drumscan be admitted to line 178 for recycling through inlet 46 with theheavy bottoms and in addition, nely ground coal may be mixed with theheavy bottoms after being admitted through inlet 180.

Thus, as the falling char reaches gyratory shelf 16, it

has been heated to a temperature of at least l600 F. and

the volatile matter has been distilled off so that it contains onlyabout 2% of volatile matter. The coal at this point is joined byrecycled char from char inlet 54 to provide the necessary heat capacityfor the system, as is explained above.

The stream of hydrogen thermal carrier gas and primary volatiles iswithdrawn through conduit l and is introduced into -knockout and tarremoval drum 136 at about 900 F. with Ithe vapor pressure of the highestboiling components about one tenth to one twentieth of system pressure.Next, the combined gas stream is subjected to vapor phase hydrogenationin sequential catalytic chambers 147, 148 and 149. Additional hothydrogen may be diverted from the main stream of thermal carrier gasthrough line 1'3-2 to conduits l130 and 150 for combination with themixed gas stream. This'further addition of hot hydrogen maintains thegas stream at lthe desired high temperature of about l000 F. andprevents any undesired condensation of valuable hydrocarbons, byincreasing the compounds) 15 Tar acids and tar bases 15 AromaticsRefractory pitch, 1boiling above 600 F 50 The fina-l coal stilldistillate, operating on bituminous coal under rather severehydrodealkylating conditions may be expected to produce a distillate oflthe following approximate analysis:

18 Oleins none Aromatics (average molecular weight less than 115) 95.0Pitch none Tar Acids none rTar bases, chiefly pyridine and quinoline 1.0Sulfur Less than 100 pp ni.

In order to illustrate the great chemical complexity of coal distillatewhich is produced 'by conventional processes,

and Vparticularly so as to point up the very distinct advantages of thecoal still system, presented herebelow is a list of the chief organiccompounds which have been identied yin coal tars and light oils. Severalof the compounds listed in column three are recovered commercially inbyproduct colte oven practice.

Column one identies many of the compounds which exist in the coal stilldistillate under mild operating conditions. Column eight lists the finalcoal still products when operating under the most severe hydrorevningand Percent hydrodealkylating conditions and indicates the initial com-Parafns 4.0 pounds from which they are derived.

Mild conditions Compound Initial compound Compound Classification Nameof compound Compound formula retained Severe conditions appearing ofcompound group under Seyer@ in straight coal still l Final coal stillrun coal still conditions M.P., Boiling distillate distillate C. point,C.

Alkane n-Pentane 36. 2 Hydrogen, methane,

ethane, etc. Naphthene Cyclopentane 49. 5} D0 Cyclo-slkene CyclopenteneC H 44. 2 Alkene Pantone-1...-- 29. 9 Do. Alkene n-Hexylene 67. 5 D o.Cyelo-olen 1-3 cyclopentadiene.. 42` 5 Do. Alkane n-Hexane 69. 0 Seinebenzene. Aromatic E tetained as benzene.

C clohexane 8 enzene. iNaphthene iThiophene gzS plus butane.

C clohexene 00H10 enzene. icycwlefm ipiethyismnde.. s2. o Hts piusethane.

Alkfirie n-Heptane C H 98. 4 Toluene. Naphthene Methyleyclohexane 100. 3Toluene or benzene. Aromatic Toluene 110. 6 Do. Naphthene 1,3 dimethyl 4121. 0 Xylene to benzene.

cyclohexane. Naphthene 1, 4 dimethyl CH12(CH3)2 No 119. 0 Do.

cyclohexane. Naphthene Cycloheptane 01H14-. 118. 1 Light hydrocarbons.Wbater soluble tar Pyrz'dzne CsHN 115. 3 Pyridine.

ase. 2methylthiophene CH3C4H3S 112. 5 HQS plus light HC's.3-metliylthiophene CHaCiHgS.- 115. 4 Do.

Alkane n-Octane CEHIL-. 125. 8 Light HCs. Allrene Octylene CgHm 123 Do.Water soluble tar 2-Picoline CHgCHiN 128 Pyridine.

base. Dirnetliyl- (CHW C4HgS 136-138 HzS plus light HCs.

thiophene. Aromatic Ethyl benzene C5H5C2H5 136. 15 Ethylene benzene orbenzene. do p-zylene C5H4(CH3)2 138.4 Xylene or benzene. do m-zyZene--C6H4(CH3)2 139.1 Do. do o-zylene CEHACHQL-. 144.4 Do.

Aromatic; arylal- Styrene CeHsCHzCHz 146 Ethyl benzene kene. onbenzene.Water soluble tar Dimethyhpyridines- (CH3)2C5H3N 143-163 Pyridine.

bases. lutidines. Armn atie Isoropylbejnzene CeHCHHg); No -96. 9 152. 4Benzene or toluene.

umene Propyl benzene. CGH5CH3C2H5 No -101. 6 2 Toluene or benzene' Ethyltoluenes CGH4CH3C2H5.. Do. i Trimethyl-thio- (CH3)3C4HS H13 plus light.

phene. HCs. Mesztylene CHMCHsk Toluene or benzene. 1,2,4 trimethyl ben-CeH3(CH3)3 Do zene (pseudocuxnene). Thiophenol H2S plus benzene. Dieyclo-pentadiene Naplithalene. n-Decane Light HCs. Coumarone Toluene orbenzene. Hemimellitene Do. isopropyl toluene Do.

(Cymenes). Indene CnH4CH2CH:CH Benzene. 1,3, diethyl benzene-CuHi(C2H5)2 Do. PheHOl a 50H D0. 1,4, diethyl benzene CnH4(CzH5)2 Do.Durene (CHaMCsHz No 80 194 Toluene, xylene, or

benzene.

Mild conditions Compound Initial compound Compound Classification Nameof compound Compound formula retained Severe conditions appearing ofcompound group under severe in straight coal s Final coal still run coalstill conditions M.P., Boiling distillate distillate C. point, C.

Tar acid 30 191.5 Toluene or benzene.

do 11 202.8 Do,

do 36 202. 5 D0.

I-lydrogenated -30 207. 2 Naphthalene.

naphthalinc.

Tar acid. (CHmCHaOH 26 211. 5 Xylcne or benzene.

Tar base m-Tolunitrile CHQCBHCN 23 v 214 N131; plus xylenc or enzcne.

, do o-Ethyl analine Cz`H5CH4NHq -43 215 Ethyl benzene or benzene.

Tar acid 2,6, xylenol 49 212 Xylene or benzene.

do 2,5 xylenol 74. 5 211.5 D0.

Hydrogenated l 1,4 dihydro-naph- -43 194. 6 Naphthalcne.

naphthaline. thalene.

Tar base 2,5 xylidine. (CHghCHsNHz 15. 5 217 Ng; plus xylcne to enzene.

dO 2,4 Xylid11e (CH3)2C5H3NH2 216 D0.

Alkane Dodecane CHa(CHn)rCH3 -12 214 Possible ring forma- Tar acidm-Ethyl phenol CzHCaH40H -4 214 Ethyl benzene t0 Jenzcne.

Tar base p-Tolunitrile CHaCtHrCN. 29. 5 217 N131; plus xylcne to Taracid p-Ethyl phenol CzHCeHrOH.- 46 219 Ethyl benzene t0 enzene.

Bicyclic aromatic.. Naphthalene C H 80.2 218 Naphthalene.

Tar ac' 2,3 xylenol (CHa)zCH3OH 75 218 Xylene to benzene.

do 3,5 xylenol (CHmCnHaOIL- 68 219 Do.

Tar base 3,5 xylidinc. (CHahCHaNHn No 221 NbHa plus xylcne to enzene.Tar acid o-Propyl phenol CaHCHrOH No 220 Pzgnpyl benzene to enzcne.Mesitol (CHmCtHZOH No 69 220 Mcsitylene tobenzenc. Thio naphthaleneCGH4SCH:CH No 32 221 HZS plus ethyl benzcne to benzene. 2,3, xylidine(CHmCHNHz No 223. 8 NH3 plus xylene to benzene. 3,4, xylenol (CHahCHrOHNo 65 225 Xylcne to benzene. m-Propyl phenol C3H1CH4OH N o 26 228 Prpylbenzene to cnzene. p-Isopropyl-phenol.. CHmCHCHrOH N o 61 229 Do.p-Propyl phenol CaHrCeHiOH No 22 232 Do. Pscudocumcnol (CHmCaHrOH N0 72235 Mesitilenc to bcnzene. Quinoline CaHrNrCHCHH... Yes -19 237Quinoline. Aromatic 2-rtnhctlhyl-naph-- CmHrCHa No 35 245 Naphthalene.

a ene. Tar base Isoqui'noline CGH4CH:NCH:CH Yes 23 243 Isoquinoline.

Quinaldine. CHrCs No 246 Quinolinc. Lepidine CHJCQHBN-- No -1 260 Do.Ditrkrlielthyl-naph- CraH(CHa)r No 255-270 Naphthalene.

a ene.

Acenaphthene C10H(CH2)2 N0 95 277.5 Do. 1naphthol 96 288 Do. 2naphthol122 295 Do.

Fluorene 116 295 Two mols benzene or one mol naphthalcne.

3-ring aromatic Phenanthrene 100 340 Phemmthrcne.

3-ring aromatic Anthraccne. 217 354 Anthracenc.

Tar base Acridz'ne 108 346 Ac'rldine.

Tar base Carbazole 246 354 NH3 plus two mols benzene or one molnaphthalene.

Yes 4-rlng aromatic Pyrene CMHm Yes 150 393 Pyrene. Yes 4-ring aromaticCM1/sane. CrrHw Yes 258 l 448 Chrysene.

Coal, freed of mineral matter, is comprised of ve elements-carbon,hydrogen, oxygen, sulfur and nitrogenwhile hydrocarbons (neutral oil)are combinations of carbon and hydrogen only. Recent studies indicatethat 92%, plus or minus 2%, of the carbon in coal is combined withhydrogen in the form of aromatic and alicyclic molecules.

For the most part, oxygen, sulfur and nitrogen in chemically functionalgroups such as OH, CO, COOH, NH2, CN, S, SH, etc., are attached to, andare integral part of, the basic very large coal molecules. After theprimary volatile matter has been allowed to condense from the vaporphase, these functional groups promote intermolecular reactivity whichresults in the progressive formation of the huge molecular structureswhich typify refractory coal tar pitch. Once allowed to form, thecomplex coal tar polymers are as diflicult to hydrogenate as is theoriginal coal itself.

The composition of primary tar is closely related to that of the coalfrom which it is distilled in that the tar saturated hydrocarbons, thechemical character and molecular Weight of coal tar changes from minuteto minute; and such instability may to some extent, persist for years.

The condensable products of all earlier processes retain oxygen, sulfurand unsaturated hydrocarbons in highly reactive forms. Therefore, theliquids produced by normal destructive distillation are constituted ofcomplex chemical combinations of literally thousands of 0rganiccompounds which cannot be separated and refined by fractionaldistillation or by routine petroleum refinery methods,

Evidently, the earlier in the pyrolysis of coal that oxygen, sulfur andnitrogen can be removed as hydrides and unsaturates stabilized in theuid stream (destructive distillation iof coal is also essentially adehydrogenating and disproportionating process), the less chemicallycomplex and the more useful is the primary'liquid product.

In the coal still with a system pressure of 15 to 30 atmospheres andwith hydrogen as the thermal carrier fluid, advantage is taken of thefact that the boiling point of a material, is effectively lowered by thefact that hydrogen effectively reduces the partial pressures of highboiling of a material component vapors. For example, as shown in thefollowing materials balance, if the condensable volatile stream inoutlet 130 per 100 pounds of M.A.F. Coal is 1/10 mol, the total hydrogenin 3.44 mols and methane is present as 0.35 mol, the partial pressure ofcondensables is evidently in the order of lo of the total systempressure or less than l pounds per square inch absolute.

As a non limiting example, the following is a summary of a materialsbalance drawn upon the Huntington Coal Still when treating EasternKentucky Elkhorn Coal, Bureau of Mines No. C-66286.

other type of catalyzing systems be positioned immediately following theprimary retort to take advantage of these temperatures. The first bed ofsolids through which the volatile system must pass is comprised of charon screen 139, which physically removes whatever liquid phasedispersoids by impingement without seriously lowering the temperatures.Such impingement and removal of resins and other liquid phase highboilers is necessary because even small amounts rapidly coat anddeactivate the catalyst.

The hydrogenation which is effected upstream from the fractionator 156removes practically all of the trou- Coal still charge, pounds per 100pounds of moisture and ash-free Coal still products, after direct vaporphase catalysis coal Component Kentucky Combustionblast, Coal stillStabilized Hydrogen lkhorn 68.5 weight perchar liquid gas (surplus) Oligas Flue gas HVAB 1 coal cent oi nitrogen distillate Hydrogen:

As combined H- A H O As NH3 As CH., (No CHl per se is thermally cracked)As free H2 Carbon:

As combined C As C As C02 from pyrolysis As CO2 from C0mbustion AS CH4Nitrogen:

As combined N 1. 5 0.50 Nil 0 8 s As tree N2 0.2 32. 59 Oxygen:

As combined O 7. 5 Nil H r 6. 49 0.32 0. 26 Nil 0.75 14.

0.1 As free O2 0.1 Sulfur:

As combined S Nil As HES 0.3 As SO2 U. 1 As sulfate Pounds per 100pounds MAF coal 100. O 47. 51 61. 35 16. 3 0. 89 15. 92 53. D5 CoalMoisture 2 7. 28 7. 28 Coal Ash 2 7. 7 7.7

1 HVAB =High Volatile A Bitmninous.

2 Moisture and ash content adjusted to American Power Company sample.

In the pressurized coal distillation process of this invention whereinthe dilution is 20 or more `moles of hydrogen per mole of coal tarvapor, coal distills at temperatures even somewhat below thoseencountered in externally heated retorts operating at atmosphericpressure. Also, it is possible to directly distill and recover somewhathigher boiling point lcompounds from coal under these conditions at 20atmospheres pressure than is conventionally possible at atmosphericpressure.

The thermal carrier iiuid will be present in an amount by Weight of twoto four times greater ,than the primary volatile matter from coaldistillation vplus the secondary volatile matter from contact cokingwhich passes out through tiue 130. Therefore, the partial pressure ofhydrogen will be high even at modest system pressures of 15 to 30atmospheres. Without a catalyzer, at these pressures, relatively littlehydrogenolysis will take place in the time available even though activehydrogenation does begin at about 750 F. In hydrogenating `suchmaterials, it has been established that maximum liquid product yield, atleast in respect to fractions in the gasoline and kerosene boilingrange, occurs between 750 F. and 950 F. when a suitable catalyst ispresent. Therefore, it is important that, in this system, a series ofmoving bed or blesome functional groups of oxygen, sulfur and nitrogenfrom the tar and many of the alkenes are saturated. However, the lowerranked hydrocarbons require more severe treatment in order tosatisfactorily dealkylate these into reformer 4stock for the productionof high octane gasoline blending stock. Therefore, a series ofsequential moving bed catalyst chambers under separate temperaturecontrol may be employed.

The stream leaving catalyst chamber 149 passes to the fractionatorsystem 156. The lighter gaseous fractions pass off through line 150 to acondensor and absorber system (not shown) which also recovers sulfurcompounds and ammonia. Stripped hydrogen with sucient methane to make upthe hydrogen requirement of the system is recycled from the condensorthrough line 116 into the methane cracking and heat exchange zone D ofthe vertical retort 10. Excess methane from the absorber may be sold asfuel gas.

As explained above, the intermediate liquid products from thefractionator system 156 as enclosed by brackets 166 may be selectivelyrecycled into the column in Zone B through selected ones of the inletsin bracket 168.

The purposes of the recycle are multifold; it gets rid of solids byrecycling heavy bottoms. If thermal exposure beyond redistillation orvaporization is required the recycle is to an upper spreader inlet 45.If destructive distillation is desired the recycle of bottoms is to thelowermost inlet 47. Also by recycling benzine and close way of notes inthe right hand column how the inspection of the iinal distillate can bepredictably modied by the recycling of selected fractions into varioushorizons of the solid fuel cascade in zone B.

COMPOUNDS COMPRISING COAL STILL DSTILLATE WHEN OPERATED FOR MAXIMUMYIELD OF STABLE, NEUTRAL DISTILLATE The Most Tliermally Stable Compoundsare Italicized Class of compound Name of compound Compound formula Molweight Melting Boiling Disposition of point, C. point, C. distillatecompounds Allmne Pantano 05H12 72 131. 5 36. 2 (Naphtliene) cycloalkane.Cyelopentane... 70 -93. 3 49. 5 LS? 2'0% 0I total Aiken@ n-Hexane--- so94. 3 e9. o S 1 a Aromatic Benzene 78 5. 5 80. 1 Either sold separatelyor recycled for alkyla- (N mii o i h s4 e 5 si 4 tion' ap ene ye o exaneAiken@ n-heptane 01H1@ 10o -9o. 5 es. 4 Rfcmd t0 dehydo' (Naphthenecycloalkane 98 -126. 4 100. 3 e' Aromatic oluene CHCHa 92 -95 110.0Added to 1gasoline blending stoc Water soluble tar base Pyridi'ne C5H5N79 -42 115.3 Removed in aqueous solution. Cycloalkane Cyeloheptane 98-12 118.1 Do 1,4,dimethy1 cyclo- 114 -86 120. 5

hexane. Recycled to dehydroge- Do 1,3,dimethyl cyclo- 114 85 121. 0 nateto xylenes.

hexane. Alkane ri-Oetane Cs 114 50. 5 125.8 Water soluble tar bases2-picolines 92 128-143 Renliotved in aqueous so u ion. Aromatic Ethylbenzene 106 93. 9 13G. 15

Do p-Xylene 106 13. 2 138. 4 Do.- m-Xylenc--. 106 53. 6 139. 1 wD0"i`i3i""z` iiiyliieimi R 1m31 29' 0 143 4 atei' so u e tar ass. me ypyr ines emove n aqueous (Lundines). solution lslglkofgt r i, AromaticIsopropyl 120 1023 5% Dimmi distiiiate, D0 Etiiyi wineries cuiiionaoin..12o 2o 162. 2-164. 9 lncudm tomem- Do 1,3,5,trimetl1yl benzeneCuH3(CHa)3 114 52; 7 104. 7

(Mesitylene) Do 1,2,4,trimethyl benzene C@H3(CH)3 114 57. 4 169. 3

(Pseudo-cumene) Allmnn ri-Derane Cmloq 144 -30 174 Aromatic IstZ-ropyltoluenes CuH4CH:(CHa)zCH3 134 -25-75- 175-176 enes Do 1,3,diethylbenzene CsH4(CzH5)z 134 -20 181. 1 Alicyclic Indcne CeHiCHiCH 116 -2182. 4 Aromatic 1,4,diethyl benzene.. CaH4(CzHs)z -35 183. 7 Recycledfor dealkyla- Do 1,2,4,5,tetrametliyl CHi(CHa)4 134 80` 194 tion anddeliydrobenzene (Durene). gcnation. Hydrogenated naplitlia-Tetrohydronaplitha- CioHi2 132 -30 207. 2

Iene. lene (Tetralin). Naphthalene Decahydro naphtha- CioIIia.. 138 -43194. 6

lene (Decalin) Alkane CH3 CH2 10CH3 170 -12 214. 5 Bicyclic aromaticCioHs 128 80. 2 218 Oilcred at 2 cents a pound for plithalic acidmanufacturing; about 20% of total distillate. Removed in aqueousC5H4N:CHCH:CH 129 -19 237. 7

soln tar base. Removed in acid Wash Isoquinoline CH4:CHNCH;CH.-.-. 12923 243 Removed in acid tar base. aqueous solution.

Do 2-methy1 quinoline CHaCpHN. 143 246 (Quinaldine). Bioyelic aromatic2-methyl naphthalene CioH1CH3 142 35 245 Removed in acid solutionRemoved in acid wash 4-Methy1 quinoline CHaCpHN- 148 0 260 Recycled.

tar base. lepidine. Aromatic Dimethylnaphthalene... CiuHt(CHa)i 156Z55-270 Alicyclic `l1uorene l CGlEIICHzCH 045 3-ring aromatic-- criantrene 14 10.... 0

D0 Anthraeene omnia.-- 17s 217 354 Aqutilofogota t Removed in acid soution 1s l l te' o ere d? Tar base Aeridine oHiCHzNoHi 10s 34s of@ C2 laPOU of 4-ring aromatic.. Pyrene mm 202 150 300 c lemma use' Do Chrysene0181112 228 258 448 1 Also used on input coal as a hydrogen transferagent.y

boiling compounds for revaporization the proportion of benzine in thevapors is increased so that benzine will be alkylated to toluene at theexpense of Xylene in catalyst chamber 149. Also dehydrogenating ofnaphthenes under selected conditions of recycle may be accomplished incatalyst chamber 148.

The following tabulation of compounds explains by blending stock for theproduction of high octane gasoline.

75 The following tabulation sets out the comparative costs ofmanufacturing high octane gasoline and illustrates the utility of thisinvention.

Catalytic cracking and alkylation; no reforming Catalytic cracking,alkylation, isomerization and reforming Case One Case Two Case ThreeCase Four No outside blend Coal still blend 1 No outside blend Coalstill blend 1 Unit Clear 3 ce. TEL Unit Clear 3 cc. TEL Unit Clear 3 ce.TEL Unit Clear 3 cc. TEL volumes F-l F-l volumes F-l F-l volumes F-l F-1volumes F-l F-l octane octane octane octane octane octane octane octaneCatalytic gasoline,

425 F. E.P 36 92 99 36+!) 94 101 3G 92 99 364-9 94 101 ropylenealkylate- 16 94 102 l6|8 104 111 16 94 102 l6+8 104 111 Reformate Poolvolume, percent F-l pool octane 78. 5 91.6 89. 4 Estimated pool cost perbbl $4. 62 $4. 90 $4. 62 Refinery output capacity, perccnt 100 100 141 1Blending of coal still distillate is limited so that the total aromaticcontent is less than 50 percent of the product gasoline.

The hot solid materials fed off gyratory shelf 16 4fall through thepartial combustion zone C. In the partial combustion zone D, the fallinghot char is contacted with oxygen and air in a controlled proportion toreact the carbon to carbon monoxide in the space below zone 56.Additional oxygen admitted through lines e0 oxydizes the carbon monoxideto carbon dioxide and the carbon dioxide passes out through ue :58 intoflue gas knockout` chamber 194. By controlling the amount of air andoxygen inlet, the percentage of the Isensible heat of combustion ofcarbon and oxygen to that contained as sensible heat of carbon dioxideexiting about 3000" F. would be 23% of the total heat of reaction ofcarbon plus oxygen to carbon dioxide. rIhe combustion chamberarrangement retains as much as 75% of the total heat of reaction assensible heat of the partially burned solid fuel. Furthermore, thesensible heat can be varied from as little as 23% of the carbon burnedto well over 75% of the heat of reaction through the dilution of theoxygen admitted through inlet 62 with nitrogen (compressed air) or othernon-reacting gas. As mentioned above, the particular details andconstruction of the combustion chamber per se are not part of thisinvention, but are fully disclosed and covered by the claims of mycopending application, Serial No. 186,920 filed April l2, 1962.

Heat transfer and methane cracking zone D serves the two statedpurposes. The thermal carrier gas is heated by absorbing most of theheat of the hot char carried on and fed downwards by gyratory shelf unit18 and, at the same time whatever methane is fed through inlet 120 isdissociated into hydrogen and colloidal carbon. Then the hydrogen, whichis substantially all of the thermal carrier gas, is bypassed throughline 122, knockout drum 126 and line 52 around the combustion zone C, sothat none of the products of combustion is entrained in the thermalcarrier gas. In this way, the mixing of the products of combustion withthe raw matter evolved in the distillation zone B is further avoided.

Methane originates from two sources in this invention. It constitutesabout half the volume of gas evolved in the destructive distillation ofcoal7 and methane is also generated in the dealkylation of the alkylatedaroma-tics. In this invention, however, no hydrogen need be wasted inthe formation of permanent hydrocarbon gases and none need be providedfrom outside sources. In order that no hydrogen leaves the system in theform of low-priced hydrocarbon gas when hydrogen gas is salable, allmethane can be recycled and thermally cracked.

The enthalphy of disassociation of methane is a rather times Itheenthalphy of disassociation is the sensible heat remaining in thethermally cracked products. This systen automatically recovers and usesnearly 60% of ithe total heat necessary to crack methane into hydrogenand carbon black and, furthermore, accomplishes the cracking bycontacting methane with a very hot annular cascade to produce all of thehydrogen necessary in the system and have the hydrogen available atsystem pressure without the necessity for compressing it.

The disassociation of methane into two volumes of hydrogen and elementalcarbon begins `slowly at 1700 F. but as the temperature is raised to2500 F. and above the disassociation is extremely rapid. For example,the rate of disassociation of methane about doubles for each F. oftemperature rises between 1800 F. and 2000 F. At any temperature thedecomposition of methane is proportionate to the time. Although pressurehas an effect on the equilibrium of hydrogen and methane, at 2500o F.and above 20 atmospheres it has little measurable effect on the kineticsup to 95% disassociation. In the present system, a residence time of'three to tive seconds finishing above 2500" F. (the temperature of thehot char y entering zone D) will disassociate approximate 95 to 98% ofthe methane which is recycled into zone D.

As the cold methane and hydrogen llow countercurrently against thecascading spent char, the char will be cooled down to a temperatureleavin-g the system of approximately 300 F.

The char entering the heat transfer and methane cracking zone D, beingfed off the periphery of gyratory shelf unit 18 can be heated toapproximately 2800 F. and, therefore, heat recovery to the thermalcarrier gas is effected as noted above by passing recycled hydrogen orhydrogen and methane countercurrently lthrough -the cascade of very hotchar. The methane and whatever C2 and C3 hydrocarbon gases will bedissociated into hydrogen and carbon as they are heated to thetemperature of the incandescent char, i.e., above l800 F. Thus the heattransfer zone also functions as a hydrogen generator as noted above.

In order to provide the necessary heat for the system as sensible heatof the char leaving zone C, either the partial combustion and heatexchange function of zones C and D must be repeated or additional solidfuel must be recycled through these zones when the yield of char is muchless than of the weight of the MAF. Coal 0r when a large proportion ofthe methane is to be cracked. In the present invention, the preferredmethod of accomplishing this is by recycling, as it would appear to beless expensive from the apparatus involved. Referring 4to FIG. 1, chartrap or collector 68 at the lower end of zone D collects that charrequired for recycle so that it may be selectively metered from thebottom of trap 68 by means of star valve 98. Excess char spills overonto the hopper 70 below and is removed from the system. The requiredamount of char per pound of raw coal to be recycled is metered by gasvalve 9S and falls to juncture 100 which in eect is a -gas lift boot.Line 108 is somewhat smaller diameter at the lower end than at the upperend for allowing chunks too coarse to become gas entrained to drop outof the circulating gas stream into a coarse removal chamber through line102 occasionally emptied by valve 104.

The axial flow fan 106 causes continuous circulation of entraining gasat system pressure upward through duct 108 and into separator 110. Thegas then passes through separating cone 112 and returns through line114. Whatever line char is metered out by star valve 98 through trap 68is entrained in the continuous gas stream and it is pneumaticallyconveyed to separator 110 where it falls through line 54 back into theseparating bed on top of gyratory shelf 16 after it has been separatedfrom the gas stream. The entrance of recycled char inlet line 54 isbelow the entrance of thermal carrier 4gas 52 so that no heat isabsorbed by recycled char from the thermal carrier.

Thus, the sensible heat capacity of the solid fuel cascade through zonesC and D may be increased any required amount, and regulation of thisamount of recycle is controlled by suitable controls of starl valve 98.

The char discharge lock 80 may be pressurized by flue gas from a takeoffof liuc 86 and thus pressurizing is controlled by an inlet valve 88 andoutlet valve 92 as well as by solid materials entrance and exit bellvalves 78 and 84. Upon attaining system pressure in the discharge lock,valve 78 may be opened to allow the passage of char or ash into thedischarge lock. Valves 78 and 84 lare then closed and the lock isde-pressurized by opening valve 92 to the atmosphere. When the dischargelock 80 has been de-pressurized, the bell valve 84 can be opened and thechar and ash can be discharged into an ash bin or char bin 94. Bufferbin 74 is proportioned such that the material accumulatingin bin 74 issomewhat less than enough to lill the discharge lock 80 so that thevalve 78 may operate freely. In order to close -valve 78 and insure itsseating free of solid materials, the valve 72 may be momentarily closed.

As a further illustrative but non-limiting example of the thermalanalysis of the described process utilizing a Kentucky Elk Horn coal:

The coal of the present example from the East Kentuckly Elkhorn No. 3bed and the MAF (moisture and ash-free) analysis is identical to theBureau of Mines sample No. 3-66286.

This coal has been subjected to destructive distillation at 932 F. andthe results of the modified Fischer carbonization assay are listed onpage 37 of the Bureau of Mines Bulletin 57.

The ultimate analysis of the coal sample is, in pounds per hundredpounds of MAF coal:

Pounds Hydrogen 5.5 Carbon 85.0 Nitrogen 1.5 Oxygen 7.5 Sulfur 0.5

Coal Moisture 7.28 Coal Ash 7.7

The caloritic value is- 15,130 B.t.u. per pound of MAF coal.

The yield of tar and light oil, when carbonized at 932 F. by theFischer-Schrader method described on pages 3-6 of USBM Bulletin 571, is42 gallons per short ton of MAF coal. Thermal solution and hydrogentransfer to active sites formed on the coal molecule during destructivedistillation, is expected to increase the Fischer Assay volume ofcondensables by some fty percent. Moreover, the bulk density of thecatalyzed condensable matter is about l5 percent less than tar and thetotal volumetric yield may approach gallons of neutral distillate perMAF ton of Elkhorn coal.

The following heat balance is drawn upon this system as shown indrawing.

This present method of carbonization provides for the hydrogenentrainment and prompt removal of volatile matter as it is distilledfrom the coal below 950 F. Following the distillation of all condensablematter from the coal, the resulting high volatile char is progressivelyheated to a temperature at which secondary distillation occurs andsubstantial devolatilization is effected. Therefore, the following heatbalance is neither strictly that of low nor of high temperaturecarbonization because the volatile matter, entrained in the hydrogenthermal carrier, leaves the carbonizing system at about 900 F. while thechar is heated to at least 1600 F. to insure adequate hydrogen recovery.

Further, in the following heat balance, no methane is cracked because anexcess of free hydrogen is produced from the secondary distillation ofthe high volatile char. However, if the market for hydrogen shouldjustify the additional expense, the product methane can be thermallycracked in the system to elemental hydrogen at a direct cost of abouteleven cents a thousand standard cubic feet.

SUMMARY AND RECAPITULATION In the following tabulations, heat isexpressed in B.t.u. (British thermal units) per pounds of moisture andash-free coal.

Coal still function A Drying and Preheating Coal to 650 F.

NoTn: Minus sign before a heat quantity denotes that which leaves thezone or is otherwise expended.

Summary of low temperature carbonization functon'B Distilling of thecoals condensable matter and heating the coal completely through itsplastic range.

B.t.u. per 100 pounds Item (B-l): MAF coal Low temperaturecarbonization, raising the dried coal and all volatiles from 650 F.through 900 F., including heat of decomposition and of vaporization21,000

Summary 0f high temperature carbonization function T Raising the highvolatile char with secondary volatiles 29 from 900 F. through 1600 F.and contact coking of recycled heavy bottoms.

Summary of coal still function C The heating of char to incandescence byits partial combustion to carbon dioxide.

B.t.u. per 100 pounds Item (C-l): MAF coal Adjusted heat losses to waterand to the surroundings Credit Item (C-Z) Sensible heat of thecombustion oxygen entering system about 50" F. (Zero pre-v heat) CreditItem (C-3):

Sensible heat of the combustion air entering the system above 50 F.(Zero preheat) Credit Item (C-4):

Sensible heat of the char above 5 0 F. cascading ofr" shelf 41 andentering the combustion zone at 1600 F. +32,500

Item (C-S) Combustion of fuel to CO2, H2O and SO2:

5.4 pounds C 14,100 B.t.u./

76,000 0.04 pounds H 51,300 B.t.u./ 45

lb. 2,060 0.1 pounds S CID 4,050 B.t.u./

Total heat generated by combustion per 100 pounds MAF coal +78,465 Item(FG-l):

Sensible heat in flue gas between 50 and 300 F 43,800 Item (SF-1): 55

Sensible heat in the carbon above 50 leaving zone D over shelf 10065,500

Summary of coal still function D B.t.u. per pounds Item (TC-l) or(iD-1): MAF coal Item (TC-1) or (D-1):

Heating 1133 SCF of hydrogen from 50 70 to 2700 F. (See Item C-4) 56,400

Item (D-2) Residual heat above 50 F. in 69.05 pounds of char including7.7 pounds of ash, leaving the system at 300 F 4,600 75 Item (D-3):

Estimated losses to cooling water and to the surroundings Item (SF 1):

Sub-total: Required sensible heat of 69.05 pounds of char availablebetween 50 F. and 3000 F. +65,500

RECAPITULATION OF THE COAL STILL Zonal zent requirement Zone A: B.t.u.

Sensible heat in 53.05 pounds of combustion Zone D flue gas above 50 F.43,800 Zones B-i-C:

Sensible heat in 1133 SCF (6.0 pounds) of thermal carrier hydrogen above50 F. 56,400 Zone E:

Residual heat in existing char plus losses 10,700 Combustion Zone D:

Generated by combustion of 5.54 pounds of MAF char +78,400 Sensible heatin char entering Zone D at NOTE: The materials balance on this coal isset out above.

While the invention has been particularly shown and described withreference to a preferred embodiment thereof, it will be understood bythose skilled in the art that various changes in form and details may bemade therein without departing from the spirit and scope of theinvention.

I claim:

1. In a process for continuous thermal treatment of coal for therecovery of values therefrom by introducing crushed coal into a verticalretort having a series of gas isolated zones and operable -atsubstantial pressures, distilling primary volatile matter from the coalin a distillation zone of said retort while utilizing hydrogen at hightemperature and system pressure as a thermal carrier iiuid foraccomplishing said distillati-on, feeding the coal to a lower gasseparated zone of said retort and partially oxidizing the char remainingfrom said distillation step while preventing the combustion products ofsaid oxidation step from entering the distillation zone, feeding theoxidized hot char to a lower gas separated zone of said retort andpassing methane through the partially oxidized hot char to disassociatethe methane into hydrogen and carbon, and passing the hot hydrogen soproduced at systern pressure into the distillation zone to be utilizedas the thermal carrier gas, the improvement that comprises; repeatingthe steps of partial oxidation of char and feeding the hot char to alowergas separated zone with a portion of the char by recycling aportion of the char from the lower portion of the lowest recited zone upto the upper portion of the zone for accomplishing partial combustion.

2. A process for the continuous thermal treatment of coal as ydeiined inclaim 1 further comprising accomplishing the recycling of a portion ofthe char by a gas lift, and removing heavy char particles from theportion of the char recycled.

3. A process for the continuous thermal treatment of coal for therecovery of values therefrom, comprising: yintroducing crushed coal intoa vertical retort having a series ofgas isolated zones and operable atsubstantial pressures, distill'ing primary volatile matter `from thecoal in a distillation zone of said retort while utilizing hydrogen athigh temperature and system pressure as a thermal carrier huid foraccomplishing said distillation, yfeeding the coal to a lower gasseparated zone of said retort and parti-ally oxidizing the charremaining from said distillation ystep While preventing the combustionproducts of said oxidation `step from entering the distillation zone,feeding the oxidized hot char to a lower gas separated zone `of said4retort and passing methane through the partially oxidized Ihot char todisassociate the methane int-o hydrogen and carbon, passing the hothydrogen so produced at system pressure in-to the distillation zone tobe utilized as the thermal carrier gas, passing the admixture of thermalcarrier hydrogen and distilled volatile matter of the coal from thedistillation zone to a catalytic `treatment zone for contact with acatalyst, fractionating the products of such catalytic treatment in afractionating zone, and the improvement that comprises selectivelyrecycling certain boiling range constituents from the fractionating zoneand re-introducing said constituents back into the distillation zone atselected predetermined horizons to accomplish further thermal treatmentof -said recycled constituents.

4. A method for the continuous distillation of coal as defined in claim3 wherein the recycled selected boiling range constituents are primarilyliquid and spraying said liquids at selected horizons into the freelyfalling coal which is incandesent, -and introducing -those constituentsrequiring the least thermal `treatment lat a higher horizon than thoserequiring a more severe thermal exposure which are introduced Iat alower horizon into the dis-tillation zone. t

5. A method for the continuous distillation of coal as defined in claim4 further comprising introducing ground coal into at least one of therecycled liquid constituents requiring severe thermal exposure andrecycling the stream containing said ground coal into the distallationzone.

6. The process of claim 3 including the step of removing the tar fromthe admixture of thermal carrier hydrogen 'and distilled volatile matterprior to its introduction into the catalytic treatment zone.

7. A process for the continuous thermal theatment of coal for therecovery of values therefrom, comprising:

introducing crushed coal into a vertical retort having a series of gasisolated zones and operable at substantial pressures, distilling primaryvolatile matter from the coal in a distillation zone of said retortwhile utilizing hydrogen at high temperature and system pressure as athermal carrier iiu-id for accomplishing said distillation,

feeding the coal to a lower gas separated zone of saidv retort andpartially oxidizing the char remaining from said distillation step whileprevent-ing the combustion products of said oxidation step from enteringthe distillation zone, feeding the oxidized hot char to `a =lower gasseparated zone of said retort, passing methane through the partiallyoxidized hot char to disassociate the methlane into hydrogen and carbon,passing the hot hydrogen so produced at system pressure in-to thedistillation zone to be utilized as the thermal carrier gas -and theimprovement comprising removing the products of distillation and thermalcarrier hydrogen to a plurality of separate catalytic zones andperforming vapor phase catalysis on said products of distillation withdifferent catalytic materials in each of the separate catalytic zones.

8. A method for the continuous distillation of coal as defined in claim7 wherein one of the several separate catalytic treatment zones is `forthe purpose of removing oxygen and sulfur and saturating the oleiins bycontacting the products of distillation and the thermal carrier hydrogenwith a suitable catalyst.

9. A method for continuous distillation of coal as detned in claim 7wherein one of the separate catalytic zones accomplishes reforming forremoving hydrogen from naphthenes to leave aromatic compounds.

10. A method for the continuous distillation of coal as detined in claim7 wherein one of the separate catalytic zones is for the purpose ofcausing an alkylation shift.

111. A process for the continuous thermal treatment of coal for therecovery of values therefrom, comprising: introducing crushed coal intoa vertical retort having a series of gas isolated zones and operable atsubstantial pressures, distilling primary volatile matter from the coalin a distillation zone of said ret-ort while utilizing hydrogen at hightemperature and sys-tem pressure as a thermal carrier fluid foraccomplishing said distillation, feeding the coial to a lower gasseparated zone of said retort and partially oxidizing the char remainingfrom said distillation step while preventing the combustion products ofsaid oxidation step `from entering the distillation zone, feeding theoxidized hot char to a lower gas separated zone of said retort andpassing methane through the partially oxidized hot char to disassociatethe methane into hydrogen and carbon, passing .the hot hydrogen soproduced at system pressure into the distillation zone to be utilized asthe thermal carrier gas, passing the admixture of -thermal carrierhydrogen and distilled volatile matter from the distillation zone to acatalytic zone for catalytic treatment, fractionating the results of thecatalytic treatment, recycling selected boiling range constitu-tents ofsaid fractionation to the distillation zone for further thermaltreatment, and treating the free talling coal by a hydrogen transferagent.

12. A method for the continuous distillation of coal ias dened in claim11 wherein the coal is pretreated by a hydrogen tranfer agent consistingessentially of phenanthrene.

13. A method for the continuous distillation of coal as defined in claim8, wherein the catalyst for removing oxygen and sulphur and saturatingthe oletins is cobalt molyibdate.

14. A process for the continuous thermal treatment of coal for therecovery of values ytherefrom comprising; feeding crushed coalvertically downward in a vertical retort having a series of gas isolatedzones and operable at substantial pressures, passing inert products ofcomibustion concurrently downward with the falling coal to raise thetemperature of the coal to about 600 F. thereby preheating the coal toexpel water andcarbon oxides, distilling primary Volatile matter fromthe coal in a distillation zone of said retort while utilizing hydrogenat high temperature and system pressure as the thermal carrier Huid foraccomplishing said distillation, feeding the coal to a lower gasseparated zone of said retort and partially oxidizing the char remainingfrom said distillation step while preventing the combustion products ofsaid oxidation step from entering the distillation zone, using thecombustion products of said oxidation step for said preheating, feedingthe Ioxidized hot char to a lower gas separated zone of ysaid retort andpassing methane through the oxidized hot char to disassociate themethane into hydrogen and carbon, passing the hot hydrogen so producedat system pressure into the distillation zone to be utilized as thethermal carrier gas, catalytically treating in a plurality of separatecatalytic zones the products of said distillation in the environment oflsaid thermal carrier fluid, fractionating the results of said catalysis`and recycling selected boiling range components to predeterminedselected horizons of the distillation zone.

References Cited by the Examiner UNITED STATES PATENTS 1,960,972 5/'1934Grimm et al. 208-8 1,972,944 9/1934 Morrell 208-8 2,115,336 4/1938Krauch et al. 208-10 2,194,186 3/1940 Pier et al. 208-10 2,657,12410/1953 Gaucher 48-197 2,658,861 -11/1953 Pevere et al. 208-8 2,662,00512/19153 Evans 208-169 2,664,390 12/1953 Pevere et al 208-8 3,075,9121/1963 Eastman et al. 208-8 3,107,985 -10/ 1963 Huntington 208-103,132,083 5/1964 Kirk 20S-l5 3,150,071 9/1964 Ciapetta et al. 208-15DELBERT E. GANTZ, Primary Examiner.

ALPHONSO D. SULLIVAN, Examiner.

H. LEVINE, Assistant Examiner.

1. IN A PROCESS FOR CONTINUOUS THERMAL TREATMENT OF COAL FOR THE RECOVERY OF VALUES THEREFROM BY INTRODUCING CRUSHED COAL INTO A VERTICAL RETORT HAVING A SERIES OF GAS ISOLATED ZONES AND OPERABLE AT SUBSTANTIAL PRESSURES, DISTILLING PRIMARY VOLATILE MATTER FROM THE COALL IN A DISTILLATION ZONE OF SAID RETORT WHILE UTILIZING HYDROGEN AT HIGH TEMPERATURE AND SYSTEM PRESSURE AS A THERMAL CARRIER FLUID FOR ACCOMPLISHING SAID DISTILLATION, FEEDING THE COAL TO A LOWER GAS SEPARATED ZONE OF SAID RETORT AND PARTIALLY OXIDIZING THE CHAR REMAINING FROM SAID DISTILLATION STEP WHILE PREVENTING THE COMBUSTION PRODUCTS OF SAID OXIDATION STEP FROM ENTERING THE DISTILLATION ZONE, FEEDING THE OXIDIZED HOT CHAR TO A LOWER GAS SEPARATED ZONE OF SAID RETORT AND PASSING METHANE THROUGH THE PARTIALLY OXIDIZED HOT CHAR TO DISASSOCIATE THE METHANE INTO HYDROGEN AND CARBON, AND PASSING THE HOT HYDROGEN SO PRODUCED AT SYSTEM PRESSURE INTO THE DISTILLATION ZONE TO BE UTILIZED AS HE THERMAL CARRIER GAS, THE IMPROVEMENT THAT COMPRISES; REPEATING THE STEPS OF PARTIAL OXIDATION OF CHAR AND FEEDING THE HOT CHAR TO A LOWER GAS SEPARATED ZONE WITH A PORTION OF THE CHAR BY RECYCLING A PORTION OF THE CHAR FROM THE LOWER PORTION OF THE LOWEST RECITED ZONE UP TO THE UPPER PORTION OF THE ZONE FOR ACCOMPLISHING PARTIAL COMBUSTION. 